a) Field of the Invention
This invention relates to a method for the separation and purification of at least one xylenol isomer useful as intermediates for medicines and agricultural chemicals, and more specifically to a method for the separation and purification of at least one xylenol isomer from a mixture containing the specific xylenol isomer along with at least one organic substance other than the specific xylenol isomer, which comprises using 1,1-di(4-hydroxyphenyl)cyclohexane as a host compound capable of selectively forming a host-guest complex (hereinafter simply called "a complex") with the specific xylenol isomer as a guest compound.
b) Description of the Related Art
For the separation and purification of at least one specific xylenol isomer from a mixture containing the specific xylenol isomer along with one or more xylenol isomers other than the specific xylenol isomer and/or one or more non-xylenol organic substances, a variety of methods are known, including, for example, simple purification of a specific xylenol isomer by recrystallization, separation of 2,5-xylenol from a mixture of 2,4-xylenol and 2,5-xylenol by a selective reaction of 2,5-xylenol with an aldehyde as disclosed in JP 64-3136 and JP 01-22832, separation of xylenol isomers from each other by adsorptive separation as disclosed in JP 08-268942, and selective recovery of 2,4-xylenol by the formation of a complex between 2,4-xylenol and a diamine compound as disclosed in JP 64-3137.
The separation by simple recrystallization can hardly separate and purify 2,4-xylenol which is low in crystallinity, although it permits separation and purification in the case of 2,5-xylenol which is high in crystallinity. Further, occurrence of microcrystals by recrystallization makes it difficult to perform filtration on an industrial scale. A further problem associated with this method is that the resulting product is not sufficient in purity.
The method, which makes use of a selective reaction between an aldehyde and a specific xylenol isomer, is applicable only for the purification of 2,4-xylenol. A problem associated with this method is that 2,5-xylenol is lost as a byproduct through its reaction with the aldehyde.
The adsorptive selection allows recovery of individual isomers. This method however involves a problem in that, for its industrial application, namely, for chromatographic fractionation or for separation and purification by a simulated moving bed permitting the chromatographic fractionation in a continuous manner, complex and costly, special facilities are needed, resulting in the need for a substantial initial cost.
Further, the method making use of the formation of a complex with a diamine permits separation and purification of 2,4-xylenol which forms a complex with the diamine compound, but can hardly separate and purify the other xylenol isomers. Another problem associated with this method resides in that it must use the diamine compound which is highly toxic.